Bio-Rad MP-50 User Manual
AG®50W and AG MP-50
Cation Exchange Resins
Instruction Manual
Table of Contents
Section 1 Introduction ..........................................1
Section 2 Technical Description...........................1
Section 3 Mechanism ............................................4
Section 4 Resin Conversion..................................7
Section 5 Instructions for Use............................10
5.1 Batch Method ...............................................10
5.2 Column Method............................................11
Section 6 Sample Protocol for
Section 7 Applications.........................................16
Section 8 Storage.................................................17
Section 9 Stability................................................17
Section 10 Product Information...........................27
Cation Exchange Resins.....................14
6.1 Determination of Total Salts
in Tap Water .................................................14
6.2 Materials .......................................................15
6.3 Protocol.........................................................15
6.4 Calculation....................................................15
6.5 Notes.............................................................16
Section 1
Introduction
AG 50W and AG MP-50 strong acid cation
exchange resins are useful for single step purification
methods, for concentrating cationic solutes, and for
analytical determinations of various mixed cationic
solutes.
Section 2
Technical Description
Strong acid cation exchange resin is available as
Analytical Grade AG 50W resin, AG MP-50
macroporous resin, and Biotechnology Grade AG 50W
resin. The Analytical Grade AG 50W resin has been
exhaustively sized, purified, and converted to make it
suitable for accurate, reproducible analytical techniques.
Biotechnology Grade AG 50W resin is analytical grade
resin which is certified to contain less than 100
microorganisms per gram of resin.
AG 50W strong acid cation exchange resin is
composed of sulfonic acid functional groups attached to
1
a styrene divinylbenzene copolymer lattice. The amount
of resin crosslinking determines the bead pore size. A
resin with a lower crosslinkage has a more open structure
permeable to higher molecular weight substances than a
highly crosslinked resin. It also has a lower physical
resistance to shrinking and swelling, so that it absorbs
more water and swells to a larger wet diameter than a
highly crosslinked resin of equivalent dry diameter. For
example, typical applications of AG 50W-X2 2%
crosslinked resin and AG 50W-X4 4% crosslinked resin
include separation or concentration of peptides,
nucleotides, and amino acids. In high percentage
crosslinkage, (AG 50W-X8 8% resin, AG-50W-X12
12% resin, and AG 50W-X16 16% resin) applications
include separation of small peptides and amino acids,
removal of cations, and metal separations. Table 1 shows
the approximate molecular weight exclusion limits in
water for resins of various crosslinkages. All AG 50W
resins are supplied in the hydrogen form, and selected
AG 50W-X8 resins are available in sodium and
ammonium forms.
Table 1. Approximate Molecular Weight Exclusion
Limits for Ion Exchange Resins in Water
Percent Approximate MW Exclusion Limit
Crosslinking for Globular Molecules
2% 2,700
4% 1,400
8% 1,000
10% 800
12% 400
AG MP-50 resin is the macroporous equivalent of
AG 50W resin. Its effective surface area approximates
35 square meters per dry gram, or 30-35% porosity.
The physical properties of the resins are listed in
Table 2. The cation exchange resins are thermally stable
and resistant to solvents (alcohols, hydrocarbons, etc.),
reducing agents, and oxidizing agents.
2
3
Table 2. Summary of the Properties of AG 50
and AG MP 50 Resins
Active Resistance Resistance
Group Thermal Solvent to Oxidizing to
(X8 Resin) Stability Stability Agents Reducing
R-SO
- Good to Very good Slowly oxidizes in Very good
3
150 °C hot 15% HN0
3
Section 3
Mechanism
In an ion exchange procedure, the counterions on the
resin are replaced by sample ions that have the same
charge. In applications involving a cation exchange
resin, such as AG 50 resin, neutral molecules and anions
do not interact with the resin. AG 50 resin is available
+
with H
, Na+, or NH
converted from one ionic form to another. Usually the
resin is used in an ionic form with a lower selectivity for
the functional group than the sample ions to be
exchanged. The sample ions are then exchanged when
introduced, and can be eluted by introducing an ion with
higher affinity for the resin or a high concentration of an
+
counterions. A resin can be
3
ion with equivalent or lower affinity. Table 3 shows the
relative selectivity of various counterions. In general, the
lower the selectivity of the counterion the more readily it
exchanges for another ion of like charge. The order of
selectivity can also be used to estimate the effectiveness
for different ions as eluants, with the most highly
selective being the most efficient. Finally, the order of
selectivity can be used to estimate the difficulty of
converting the resin from one form to another.
Conversion from a highly selected to a less highly
selected form requires an excess of the new ion.
4
5
Table 3. Relative Selectivity of Various
Counterions
Counterion for AG 50W-X8 Resin Counterion for AG 50W-X8 Resin
+
H
+
Li
+
Na
+
NH
4
+
K
+
Rb
+
Cs
+
Cu
+
Ag
2+
Mn
2+
Mg
Relative Selectivity Relative Selectivity
1.0 Fe
0.85 Zn
1.5 Co
1.95 Cu
2.5 Cd
2.6 Ni
2.7 Ca
5.3 Sr
7.6 Hg
2.35 Pb
2.5 Ba
2+
2+
2+
2+
2+
2+
2+
2+
2+
2+
2+
2.55
2.7
2.8
2.9
2.95
3.0
3.9
4.95
7.2
7.5
8.7
Large mesh material (20-50 and 50-100 mesh) is
used primarily for large preparative applications and
batch operations where the resin and sample are slurried
together. Medium mesh resin (100-200 mesh) is used
primarily in column chromatography for analytical and
laboratory scale preparative applications. Fine mesh
material (200-400 and minus 400 mesh) is used for high
resolution analytical separations.
Table 4. Wet Mesh and Equivalent Micron
Diameters
Wet Mesh
(U.S. Standard) 16 20 40 50 80 100 140 200 270 325 400
µm Diameter
(1 µm=0.001msm) 1,180 850 425 300 180 150 106 75 53 45 38
The AG 50 resins are available in several particle
size ranges. The flow rate in a chromatographic column
increases with increasing particle size. However, the
attainable resolution increases with decreasing particle
size and narrower size distribution ranges. Particle size is
given either in mesh size or micron size. The larger the
mesh size number, the smaller the particle size. Table 4
shows wet mesh and equivalent micron diameters.
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Section 4
Resin Conversion
Table 5 outlines common techniques for converting
ion exchange resins from one ionic form to another.
Resin conversion is most efficiently carried out in the
column mode. However, when choosing a column,
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